Both are okay. But some other discussions with some other similar sentences about during and standing point out that sitting and standing are used as an adjective here. I.e. You are (in a) sitting (state). Hindi seems to use the perfect for this, some others said. After all, the process of sitting down is over, i.e. moving down from a standing position. I English we say: the candle is burning (right now) and after an hour we say 'the candle is burned' i.e. finished. For some reason we don't say that with 'sit': We can say 'They are sitting down now' and then after a few seconds: They have sit down', but usually we simply say 'They are sitting'. But Hindi is stricter here: they say 'They sat (down) or have sit (down)'.